Endoscopic cutting instruments having improved cutting efficiency and reduced manufacturing costs

ABSTRACT

The present invention is directed to improving the cutting efficiency and reducing the manufacturing costs associated with endoscopic cutting instruments by eliminating the distal bearing surfaces or providing means for making the contact at the distal bearing intermittent so that surfaces do no undergo high localized heat and galling. In one embodiment, this goal is achieved by modifying or removing the axial constraints on the inner sliding member that are characteristic of conventional endoscopic shavers. In another embodiment, the improved cutting efficiency and reduced manufacturing cost is achieved by eliminating a closed end characteristic of conventional endoscopic shavers (e.g., removing the closed end of either the inner sliding member or the outer sliding member to thereby eliminate the associated bearing surface formed therebetween).

PRIORITY

This application claims the benefit of U.S. Provisional Application Ser.Nos. 60/964,590, filed Aug. 13, 2007, and U.S. Provisional ApplicationSer. No. 61/011,828, filed Jan. 22, 2008, the contents of which areincorporated by reference herein in their entirety.

This application also claims the benefit of U.S. patent application Ser.No. 11/634,102, filed Dec. 6, 2006, which, in turn, claims the benefitof U.S. Provisional Application Ser. No. 60/831,986, filed Jul. 19,2006, both of which are incorporated by reference herein in theirentirety

TECHNICAL FIELD OF THE INVENTION

The present invention relates generally to the field of endoscopictissue resection and powered surgical instruments for use therein, moreparticularly to minimally invasive endoscopic cutting instruments havingimproved cutting efficiency and reduced manufacturing costs. Inparticular, the present invention teaches the elimination of ormodification to the distal bearing surface of such instruments, therebyeliminating or substantially reducing the high localized heating andgalling that is characteristic of conventional endoscopic shaverdevices.

BACKGROUND OF THE INVENTION

In contrast to conventional surgery, which requires a relatively largeincision in order to gain access to a surgical site within a body,endoscopic procedures utilize natural passages, or, alternatively,involve the formation of very small portals to gain access to thesurgical site of interest. Accordingly, an endoscopic procedure is oftenreferred to as minimally invasive surgery. One advantage of performingendoscopic surgery is that since the portions of the body that are cutare reduced, the portions of the body that need to heal after thesurgery are likewise reduced. Still another advantage of endoscopicsurgery is that it exposes less of the interior tissue of the body tothe open environment. This minimal opening of the body lessens theextent to which its internal tissue and organs are open to infection.

Advancements in this field of “closed” surgery, such as arthroscopy and,more generally, endoscopic surgery, have led to the creation of numerousminimally invasive surgical cutting instruments. As noted above, inclosed surgery, access to the surgical site is gained via one or moreportals. As such, the instruments used in the surgical procedure must besufficiently flexible, smooth and elongated to permit the distal ends ofthe instruments to reach the surgical site with minimal trauma toneighboring tissues. One end of the instrument, often referred to as the“distal end”, is designed to be positioned at the surgical site. Theopposed end of the instrument, often referred to as the “proximal end”,extends out of the patient's body. The distal end of the instrument istypically provided with some type of working head designed to manipulatethe tissue against which it is placed whereas the proximal end of theinstrument is provided with a mechanism for the user to remotely controlthe working head.

Surgical cutting instruments for use in closed surgery—often referred asendoscopic “shavers”—are typically composed of a pair of concentricallydisposed, close-ended, generally tubular members, more typically anelongated outer tubular member terminating in a distal opening or“cutting window”, an aperture situated in the distal end, on the distalend side wall, or both, and an elongated inner tubular member, slidablyand concentrically disposed in the outer tubular member, whose distalend is disposed adjacent the cutting window of the outer tubular member.The distal end of the inner tubular member typically has a surface oredge for engaging tissue via the distal opening in the outer tubularmember and cooperates with the opening to shear, cut or trim tissue, aprocess often referred to as “resection”. For example, the inner tubularmember may be rotatably driven about its axis from its proximal end by ahandpiece having a small electric motor which is controlled by one ormore finger actuated switches on the handpiece, one or more footswitches on a console supplying power to the handpiece, or some otheranalogous control means. Cut tissue can then be aspirated through thehollow lumen of the inner tubular member to be collected via a vacuumtube communicating with the handpiece. The distal end of the innertubular member can be provided with a number of dimensions orconfigurations, depending upon the surgical procedure to be performed.Similarly, the opening in the distal end of the outer tubular member maybe adapted to cooperate with the particular configuration of the distalend of the inner tubular member. For example, the inner and outertubular members can be configured to produce side cutting or endcutting, or a combination of the two, to cut soft or bony tissues orcombinations thereof. These various configurations are generallyreferred to in the art as “shaver blades”.

The cutting windows of a shaver each have perimeters composed of tworelatively longitudinal, straight or curvilinear edges connected attheir proximal ends and distal ends by two relatively transverse edges.The configuration of the longitudinal edges, and to a lesser extent thetransverse edges is determined by the intended use of the shaver. Forinstance, shavers intended for use on soft tissue will be provided withcutting windows configured for increased resection efficiency butrelatively low resistance to deformation since the cutting forces aretypically low. Conversely, those shavers intended for use on toughtissue, such as meniscus or vertebral discs, will be provided with agreater resistance to deformation since the cutting forces are quitehigh.

Resection of tissue by a shaver blade is typically accomplished by thecooperative interaction between the sharp beveled edges of the inner andouter cutting windows. As the inner and outer windows come intoalignment, vacuum within the lumen of the inner member aspirates tissueinto the opening formed. Continued rotation of the inner member causesthe inner cutting edges to approach the outer cutting edges. Tissue inthe cutting window between the inner and outer edges is either trappedbetween the edges or ejected from the window. Tissue trapped between theedges is either cut by the edges as they approach each other or torn bythe cutting edges as they pass and rotate away from each other. Theresected tissue is then aspirated from the site through the inner lumenof the inner member.

Resection efficiency can be improved by decreasing the relative portionof the material that is ejected from the window, and increasing theportion that is trapped between the edges and resected. Decreasing therelative portion ejected from the window can be achieved through the useof sharper cutting edges. Illustrative means for increasing thesharpness of the cutting edge include decreasing the included angle ofthe cutting edge, decreasing the edge radius, and decreasing theroughness of the surfaces over which tissue must slide during resection.For example, U.S. Pat. No. 5,843,106 (Heisler) discloses a shaver withincreased resection efficiency produced by an outer cutting windowconfiguration having “sharpened” low included-angle cutting edges. Therelative portion of tissue ejected from the window during closure mayalso be decreased by adding teeth to either the inner cutting edges orouter cutting edges or both. Shavers having inner cutting edges withteeth are described in the art, for example in U.S. Pat. No. 5,217,479(Shuler) and U.S. Pat. No. 5,269,798 (Winkler), each of which discloseshavers having inner cutting edges with teeth, such teeth being formedby a “through-cutting” process, such as wire electrical dischargemachining (wire EDM), or by grinding. Teeth so formed are efficient atretaining tissue within the window so that it can be cut by the lowincluded angle outer cutting edges as the inner and outer edgesconverge. The inner cutting edges do little cutting since the teeth forma very large included angle cutting edge.

The Cuda™ by Linvatec Corporation (Largo, Fla.) and the Tomcat™ byStryker Corporation (Kalamazoo, Mich.) each have teeth on both the innerand outer cutting edges, the edges being formed by a two-dimensional,through-cutting process such as grinding or wire EDM. The edges formedhave large included angles, a geometry that is inefficient for cuttingtissue. Shavers having these two-dimensionally shaped teeth on the innerand outer cutting edges separate tissue principally by tearing as theedges pass each other when the cutting window is closed. Such tearing isundesirable since the torn tissue frequently becomes trapped in the gapbetween the inner and outer tubular members, thereby causing clogging.This problem is specifically addressed in U.S. Pat. No. 6,053,928 (VanWyk et al.), which discloses a shaver having a plurality of teeth on thelaterally opposed cutting edges of an outer window, the cutting edgesbeing symmetrical when viewed in a plane normal to the axis of the tube.The cutting edges are formed so that, when viewed in any such plane, theedges have low included angles, in the valleys between the teeth as wellas the teeth. The Great White™ shaver by Linvatec, constructed inaccordance with the principles of the '928 patent, is very efficient atresecting tissue and experiences reduced clogging due to the sharpnessof the outer cutting edges.

When a shaver is used with a constant rotation imparted to the innermember, tissue in close proximity to the window is sucked into thewindow and either resected or ejected from the window in the mannerpreviously herein described. Tissue that is ejected from the window, orthe remaining tissue adjacent to a resected portion, is swept in thedirection of the rotation. When the cutting window is opened again bythe rotation of the inner member, the amount of tissue which will bepulled into the window by vacuum in the inner lumen is diminished fromthat of the previous opening event because of this directional “set” ofthe tissue. That is, because the tissue is already preferentiallyoriented in the direction of the rotation of the approaching innercutting edge, it is difficult for that inner cutting edge to getsufficient “bite” to retain the tissue in the cutting window forresection. Because of this, arthroscopic shavers are generally used inan “oscillate” mode when cutting tissue. In this mode the inner isrotated in one direction for a predetermined number of revolutions,whereupon its rotation is reversed for the same predetermined number ofrevolutions. The inner cutting edges approach the tissue fromalternating directions thereby greatly increasing the relative portionof tissue that is sucked into the window and is resected rather thanejected.

As noted above, a conventional (prior art) shaver blade assembly iscomposed of a stationary outer assembly and an inner assembly. The innerassembly is typically composed of a generally tubular member with aclosed distal end and a proximal-end hub configured for removablecoupling a drive mechanism of a powered handpiece so as to transmitrotational motion from the handpiece to the distal end of the innerassembly. The outer assembly is typically composed of a generallytubular member with a closed distal end and a proximal hub means forremovably mounting the shaver blade assembly in a powered handpiece. Anelastic member transmits an axial force distally on the inner assemblyso that contact is maintained between the outer surface of the distalend of the inner member and the inner surface of the distal end of theouter member, the surfaces together functioning as a bearing. In someshaver systems, the elastic member is a spring affixed to the hub of theinner assembly. In other systems, the elastic member is a spring in thehandpiece in which the shaver is mounted. The distal bearing surfacesare spherical on most (almost all) shavers, although shavers with othershapes are produced for specialized purposes. The radius of thespherical inner surface of the outer member is slightly larger than thatof the spherical external surface of the inner member. The applicationof the axial force to the inner member by the elastic member createsquite high Herzian contact stresses at the bearing surfaces. Sinceshavers are used with rotational speeds as high as 5,000 rpm, chafing orgalling of these surfaces is frequently a problem. To prevent galling,the materials of the inner and outer distal ends are carefully selectedand the components hardened and machined to very precise shapes,frequently with form tolerances of as little 0.0002 inches. The surfacefinishes of the bearing surfaces are also critical since irregularitiesin the surfaces can lead to high localized stresses which result ingalling of the surfaces during use. Galling of the bearing surfacesduring use creates metallic debris which can be deposited into thesurgical site, with negative consequences to the patient. In severecases, galling may cause welding of the inner and outer members so as tomake the shaver unusable. As a result, some manufacturers coat the innermember bearing surface with a gall-resistant metallic material, whileothers make the distal end of the inner member from a gall resistantalloy. In any event, galling and metallic debris created by shaverblades is still a frequent problem since inspection of the inner surfaceof the outer member is very difficult and minor manufacturingabnormalities can create surfaces which are not to specification.Because of these and other factors, forming of the inner and outerdistal end bearing surfaces is a significant portion of the shaver blademanufacturing costs.

Closely related to arthroscopic shavers is a category of devices knownin the art as arthroscopic burs, which are used for resecting bone. Bursdiffer from shavers in that the inner member has multiple cutting edgesarranged on a rotating element (the bur head), with cutting achievedsolely by the inner cutting edges. While shavers cut by cooperativeinteraction of the inner and outer cutting edges, burs cut with theinner edges only. Also, shavers use a vacuum to draw tissue into acutting window for resection while burs use suction only to removedebris from the surgical field. Burrs are ineffective for cutting softtissue. Typical burrs are the Spherical Burr, Oval Burr, Cyclone Burr,and Vortex Router by Conmed Corporation (Utica, N.Y.). The axial bearingsurface of a burr is not at the distal tip since the outer tube end isnot closed, but rather is proximally located and is formed by adissimilar material pair formed by a proximal surface of the outer hubassembly and a distal surface of the inner hub assembly. Burrs areineffective for resecting soft tissue.

The Helicut™ burr by Smith and Nephew Incorporated (Andover, Mass.), andthe Lightning™ by Conmed Corporation are specialty burrs which cut bothsoft tissue and bone. The instruments have a helical rotational innermember with two cutting edges, and an open-ended outer member with edgeswhich cooperatively resect soft tissue with the edges of the innermember. The resected tissue is removed from the site by the action ofthe helical inner as well as by a vacuum applied to the proximal end ofthe outer member. The Helicut and Lightning are unique in that theyresect both bone and soft tissue, and do not have a tubular innermember. The axial bearing surface of these devices is not at the distaltip since the outer tube end is not closed, but rather is proximallylocated and is formed by a dissimilar material pair formed by a proximalsurface of the outer hub assembly and a distal surface of the inner hubassembly. The resection efficiency of these blades having a helicalinner is quite low when cutting soft tissue since there are no teeth onthe inner or outer member to aid in preventing tissue ejection as thecutting edges approach.

Arthroscopic cutting instruments may be divided into two categories:those with tubular inner members which have an axial bearing formed bythe closed distal ends of the inner and outer tubes, and those which donot have tubular inner members and whose axial bearings are proximallylocated.

Thus, there are a number of commercially available embodiments ofpowered endoscopic cutting instruments. Nevertheless, despite the abovedescribed improvements, there remains a clear need in the art toincrease the efficiency of endoscopic cutting instruments and shaverblades and to reduce their manufacturing costs. The present invention isdirected to these needs.

SUMMARY OF THE INVENTION

In view of the foregoing, it is a primary object of the presentinvention to provide an endoscopic shaver assembly having improvedcutting efficiency and reduced manufacturing costs.

In the context of the present invention, endoscopic cutting instrumentis characterized by an elongated inner member axially slidable androtatably situated within an elongated stationary outer member, whereinboth inner and outer members have at their distal ends cutting apertureswhich cooperate to resect tissue during endoscopic surgical procedures.As noted above, prior art shavers with tubular inner and outer distalassemblies maintain axial positioning between the assemblies by applyinga distal force to the inner assembly so that the closed distal end ofthe inner member maintains contact with the distal inner surface of theouter assembly. The two surfaces together form a distal bearing, withthe distal force being supplied by a compression spring, either a partof the shaver assembly or the handpiece into which the shaver isremovably mounted. Contact stresses (Hertzian in the case of sphericalsurfaces) at the distal bearing surfaces can be high and can causegalling and generation of metallic debris if the surfaces are improperlydesigned or formed. It is a primary goal of the instant invention toeliminate this distal bearing, or provide means for making the contactat the distal bearing intermittent so that surfaces do not undergo highlocalized heating and galling.

In one embodiment, this goal is achieved by means of an open-ended tube.For example, the distal end of the outer tube, rather than being closedas is characteristic of conventional endoscopic shavers, is open whilethe distal end of the inner tube is closed. The opposite configuration,wherein the distal end of the inner tube is open while the distal end ofthe outer tube is closed, is also contemplated. In this configuration,the axial bearing then becomes proximally located. By eliminating distalbearing surfaces, the present invention provides a substantial reductionin manufacturing costs. However, in addition to eliminating distalbearing forces and reducing manufacturing costs associated therewith,removing the closed distal end of one of the tubular members can alsoimprove cutting efficiency. For example, by removing the closed distalend of the outer tube that is typical of prior art shavers, one canprovide additional tissue access to the inner cutting window.

In an alternate embodiment, this goal is achieved by means of afree-floating inner member. It was discovered herein that allowing theinner member to axially “float” resulted in an increase in the resectionefficiency of a shaver. Specifically, with a free floating inner member,the teeth on the inner cutting edge able to preferentially find regionsof least resistance (i.e., the “sweet spot” in which the cutting edge isable to most easily penetrate tissue) to thereby minimize the ejectionof tissue from the cutting window. In contrast to prior art shavers, inwhich the position of teeth on the cutting edge is fixed relative to theposition of the outer member and tissue in proximity therewith such thatthe inner and outer edge teeth intersect the tissue repeatedly in agiven location, the teeth on the endoscopic shaver of the presentinvention are able to contact the tissue in random locations so as toenhance tooth penetration. A shaver formed in accordance with theprinciples of the present invention does not have a bearing, but ratherstops which limit axial travel of the inner member. Elimination of thebearing with its associated high manufacturing costs allows the shaverto be produced at low cost. Elimination of the distal bearing, with itsassociated proclivity for generation of metallic debris by galling ofthe bearing surfaces, also reduces metallic debris.

In this alternate embodiment, the distal axial force applied to theinner assembly and thus the corresponding the distal bearing surface iseliminated by removing or reducing the axial constraints on the innermember that are characteristic of conventional endoscopic shavers,allowing it to travel unrestricted within predetermined limits. Forexample, proximal movement of the inner assembly may be limited by oneor more coordinating features in the handpiece, the inner hub and/or inthe outer hub. Distal movement of the inner assembly may be limited bycontact between the outer surface of the inner assembly distal end andthe inner surface of the outer assembly distal end, the surfacesfunctioning as a stop rather than a bearing, or by contact between theproximal surface of the outer member hub and the distal surface of theinner member hub, with or without the inclusion of a proximallypositioned spacer positioned therebetween. When the distal limit is dueto a spacer between the inner and outer hubs, it is preferable toprovide a predetermined minimum gap between the outer surface of theinner assembly distal end and the inner surface of the outer assemblydistal end, thereby preventing contact therebetween that may result inunintended heating or galling.

In yet another embodiment, the distal bearing is replaced by a proximalbearing, the bearing consisting of a wear-resistant spacer between theinner and outer hubs. A distal axial force applied by a spring maintainscontact between the hubs and the spacer. A gap is maintained betweendistal outer surface of the inner distal member and the inner surface ofthe closed distal end of the outer distal member.

In yet a further embodiment, the spacer of the previous embodiments isreplaced by a cam and follower affixed to the inner and outer hubs. Thecam and follower cooperatively determine the axial position of the innerassembly within the outer assembly. In one form, contact between the camand follower is constant so that the bearing is always formed by the camand follower surfaces and a predetermined gap is maintained at thedistal end. In another form the distal bearing surfaces are in contactexcept when the inner assembly is displaced proximally by cooperativeinteraction between the cam and follower. In a preferred embodiment, theinner assembly is displaced axially twice in each revolution of theinner, each displacement being 20 degrees or more of rotational angle.Other displacement frequencies and durations may be used. Periodicseparation of the distal bearing surfaces allows cooling of thecontacting surface portions, and contamination of these portions bysaline solution and tissue. Contaminants on the bearing surfaces act aslubricants minimizing or eliminating galling and the generation ofmetallic debris.

It is, accordingly, an object of the present invention to reducemanufacturing costs by the elimination of or modification to the distalend axial bearing.

It is further an object of the present invention to provide a shaverhaving reduced opportunity for galling and metal shedding by eliminatingthe distal end axial bearing.

It is also an object of the present invention to facilitate a shavermanufacture through the elimination of critical distal bearing surfacefeatures which, under conventional practices, must be formed to closetolerances and which are difficult to inspect.

It is also an object to provide an endoscopic shaver assembly with highresection efficiency, wherein tissue ejection is reduced by means of anaxially floating inner member which allows the inner cutting edge tomore efficiently engage tissue, or wherein tissue access to the cuttingwindow is increased through the removal of the outer tube closed end, ora combination of the two.

Accordingly, in one embodiment, the present invention provides anendoscopic surgical assembly characterized by a concentrically disposedelongated tubular inner and outer members, each of said elongatedmembers comprising a coordinating hub disposed at its proximal end, alaterally disposed cutting aperture at its distal end, and a centrallumen extending therebetween, said inner member being sized to beslidably received within the lumen of said outer member, wherein whensaid inner and outer hubs are connected, axial displacement between theinner and outer members is fixed and the respective cutting apertures ofsaid inner and outer members are aligned to permit cooperative resectionof tissue in contact therewith, further wherein

(a) the inner member comprises a distally facing open end while thedistally facing end of the outer member comprises a closed surface, or

(b) the outer member comprises a distally facing open end while thedistally facing end of the inner member comprises a closed surface.

In an alternate embodiment, the present invention provides an endoscopicsurgical assembly characterized by concentrically disposed tubularelongated inner and outer members, each of said elongated memberscomprising a coordinating hub disposed at its proximal end, a laterallydisposed cutting aperture at its distal end, and a central lumenextending therebetween, said inner member being sized to be slidablyreceived within the lumen of said outer member, wherein axial force onsaid inner member is eliminated, thereby permitting said inner member tomove axially within predetermined limits, further wherein when saidinner and outer hubs are connected the respective cutting apertures ofsaid inner and outer members are aligned to permit cooperative resectionof tissue in contact therewith but the distal ends of the inner andouter members do not form a distal bearing surface.

In yet another embodiment, the present invention provides an endoscopicsurgical assembly characterized by concentrically disposed elongatedtubular inner and outer members, each of said elongated memberscomprising a coordinating hub disposed at its proximal end, a laterallydisposed cutting aperture at its distal end, and a central lumenextending therebetween, said inner member being sized to be slidablyreceived within the lumen of said outer member, wherein:

(a) the inner member hub includes an elastic member that transmits anaxial force distally on said inner member so as to constrain proximalmovement thereof,

(b) the proximal end of the outer member hub is characterized by anouter collar concentrically disposed about an inner stem, said assemblyfurther comprising an annular spacer element positioned between theproximal end of the inner stem and the distal end of the inner memberhub so as to prevent direct contact therebetween; and

(c) when said inner and outer hubs are connected the distal ends of theinner and outer members do not form a distal bearing surface.

The above assemblies may be modified to include or used in connectionwith one or more aspiration and/or irrigation means. They may further bemodified to include or used in connection with conventional poweredhandpiece assemblies and/or drive mechanisms to facilitate operation.The present invention accordingly provides methods of using theendoscopic surgical assemblies of the present invention in the field of“closed” surgery, such as arthroscopy and, more generally, endoscopicsurgery.

In a preferred embodiment, the concentrically disposed inner and outermembers of the endoscopic surgical assembly comprise concentric tubesprovided with laterally disposed cooperating cutting windows. In onepreferred embodiment, the inner member is provided with a closed endwhile the outer tube is provided with an open end. In an alternatepreferred embodiment, it is the inner member that is open ended whilethe outer member is closed.

In a preferred embodiment, each cutting window is provided with aperimeter comprised of two longitudinal cutting edges and at least one,possibly two transverse cutting edges. The cutting edges may be linear,curvilinear or a combination thereof, thereby providing the cuttingwindow with an overall shape that is regular or irregular, symmetricalor asymmetrical shape. Examples of suitable cutting window shapesinclude, but are not limited to, circles, ellipses, polygons such asrectangles, squares, rhomboids, trapezoids, and the like, as well asportions and combinations thereof.

While the present invention is not limited to cutting windows of anyparticular size, shape and dimension, in order to achieve efficientcutting, it is preferable that at least a portion of one or more cuttingedges is angled or beveled so as to yield a sharp cutting surface. Asuitable included angle for the beveled cutting edges preferably rangesfrom 15 to 70 degrees, and more preferably ranges between 20 and 50degrees.

These and other objects are accomplished in the invention hereindescribed, directed to an endoscopic shaver blade having improvedcutting efficiency. Further objects and features of the invention willbecome more fully apparent when the following detailed description isread in conjunction with the accompanying figures and examples. However,it is to be understood that both the foregoing summary of the inventionand the following detailed description are of a preferred embodiment,and not restrictive of the invention or other alternate embodiments ofthe invention. In particular, while the invention is described hereinwith reference to a number of specific embodiments, it will beappreciated that the description is illustrative of the invention and isnot constructed as limiting of the invention. Various modifications andapplications may occur to those who are skilled in the art, withoutdeparting from the spirit and the scope of the invention, as describedby the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a disassembled view of a prior art arthroscopic shaver bladeassembly.

FIG. 2 is an exploded view of the inner and outer assemblies of theprior art arthroscopic shaver blade assembly of FIG. 1.

FIG. 3 is a plan view of the prior art arthroscopic shaver bladeassembly of FIG. 1.

FIG. 4 is a side elevational sectional view of distal portion of thearthroscopic shaver blade assembly of FIG. 1, at location B-B of FIG. 3.

FIG. 5 is a side elevational sectional view of the proximal portion ofthe arthroscopic shaver blade assembly of FIG. 1, at location A-A ofFIG. 3.

FIG. 6A is a disassembled view of an open-ended shaver blade assemblyformed in accordance with the principles of the present invention.

FIG. 6B is an exploded view of the inner and outer assemblies of theopen-ended shaver assembly of FIG. 6A.

FIG. 7 is a plan view of the open-ended shaver assembly of FIG. 6.

FIG. 8 is a side elevational sectional view of the distal portion of theopen-ended shaver assembly of FIG. 6, at location A-A of FIG. 7.

FIG. 9 is a side elevational sectional view of the proximal portion ofthe open-ended shaver assembly of FIG. 6, at location B-B of FIG. 7.

FIG. 10 is a plan view of the distal end of an alternate embodiment ofthe open-ended shaver assembly of FIG. 6.

FIG. 11 is a side elevational view of the objects of FIG. 10.

FIG. 12 is a perspective view of the objects of FIG. 10.

FIG. 13 is an exploded view of the inner and outer assemblies of analternate embodiment of an open-ended shaver assembly formed inaccordance with the principles of the present invention.

FIG. 14 is a plan view of the open-ended shaver blade assembly of FIG.13.

FIG. 15 is a side elevational section view of the distal end of theopen-ended shaver assembly of FIG. 13, at location B-B of FIG. 14.

FIG. 16 is a side elevational sectional view of the proximal end of theopen-ended shaver assembly of FIG. 13, at location A-A of FIG. 14.

FIG. 17A is a plan view of a free-floating shaver assembly formed inaccordance with the principles of the present invention.

FIG. 17B is a side elevational view of the free-floating shaver assemblyof FIG. 17A.

FIG. 17C is a perspective view of the free-floating shaver bladeassembly of FIG. 17A.

FIG. 18A is a plan view of the free-floating shaver blade assembly ofFIG. 17, depicting the inner assembly in its most distal position.

FIG. 18B is a side elevational sectional view of the distal portion ofthe free-floating shaver assembly of FIG. 17, at location B-B of FIG.18A.

FIG. 18C is a side elevational sectional view of the proximal portion ofthe free-floating shaver assembly of FIG. 17, at location A-A of FIG.18A.

FIG. 19A is a plan view of the free-floating shaver assembly of FIG. 17,depicting the inner assembly in its most proximal position.

FIG. 19B is side elevational sectional view of the distal portion of thefree-floating shaver assembly of FIG. 17, at location B-B of FIG. 19A.

FIG. 19C is a side elevational sectional view of the proximal portion ofthe free-floating shaver assembly of FIG. 17, at location A-A of FIG.19A.

FIG. 20A is a plan view of an alternate embodiment of a free-floatingshaver assembly formed in accordance with the principles of the presentinvention, depicting the inner assembly in its most proximal position.

FIG. 20B is a side elevational sectional view of the distal portion ofthe free-floating shaver assembly of FIG. 20A, at location A-A thereof.

FIG. 20C is a side elevational sectional view of the proximal portion ofthe free-floating shaver assembly of FIG. 20A, at location B-B thereof.

FIG. 21A is plan view of the free-floating shaver assembly of FIG. 20A,depicting the inner assembly in its most distal position.

FIG. 21B is a side elevational sectional view of the distal portion ofthe free-floating shaver assembly of FIG. 21A, at location A-A of FIG.21A.

FIG. 21C is a side elevational sectional view of the proximal portion ofthe free-floating shaver assembly of FIG. 21A, at location B-B of FIG.21A.

FIG. 22A is a plan view of an alternate embodiment of a shaver assemblyformed in accordance with the principles of the present invention,depicting the inner assembly in its most distal position.

FIG. 22B is a side elevational sectional view of the distal portion ofthe shaver assembly of FIG. 22A, at location A-A thereof.

FIG. 22C is a side elevational sectional view of the proximal portion ofthe shaver assembly of FIG. 22A, at location B-B thereof.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Although any methods and materials similar or equivalent to thosedescribed herein can be used in the practice or testing of embodimentsof the present invention, the preferred methods, devices, and materialsare now described. However, before the present materials and methods aredescribed, it is to be understood that the present invention is notlimited to the particular sizes, shapes, dimensions, materials,methodologies, protocols, etc. described herein, as these may vary inaccordance with routine experimentation and optimization. It is also tobe understood that the terminology used in the description is for thepurpose of describing the particular versions or embodiments only, andis not intended to limit the scope of the present invention which willbe limited only by the appended claims.

Unless otherwise defined, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which the present invention belongs. However, in case ofconflict, the present specification, including definitions, willcontrol.

In the context of the present invention, the following definitionsapply:

The words “a”, “an” and “the” as used herein mean “at least one” unlessotherwise specifically indicated. Thus, for example, reference to a “camlobe” is a reference to one or more cams and equivalents thereof knownto those skilled in the art, and so forth.

The term “proximal” as used herein refers to that end or portion whichis situated closest to the user of the device, farthest away from thetarget surgical site. In the context of the present invention, theproximal end of the inventive device includes the handpiece region.

The term “distal” as used herein refers to that end or portion situatedfarthest away from the user of the device, closest to the targetsurgical site. In the context of the present invention, the distal endof the inventive device includes the respective cutting windows of theinner and outer tubular members.

The term “rotational” as used herein refers to the revolutionarymovement about the center point or longitudinal axis of the device. Inthe context of the present invention, rotation of the elongated innertubular member relative to the elongated outer tubular member, whichtypically is held in a stationary position, results in relative rotationof their respective cutting apertures which coordinate to resect targettissue within the surgical site of interest.

The term “axial” as used herein refers to the direction relating to orparallel with the longitudinal axis of the device. In the context of thepresent invention, relative axial movement between the elongated outertubular member and the elongated inner tubular member slidably receivedtherein results in improved cutting efficiency. The present inventioncontemplates the combination of relative axial displacement and relativerotational motion to enhance cutting efficiency. Means for automatingsuch axial and rotational movement are described in U.S. PatentPublication No. 2008-0021487-A1 to Heisler (hereinafter USPP '487), theentire contents of which are incorporated herein by reference.Specifically, where appropriate, the endoscopic cutting instruments ofthe present invention may be modified to include the means forautomating axial movement with rotation motion described in USPP '487.

The present invention makes reference to “bearings” and “bearingsurfaces”. The terms “bearing” and “bearing surface” refer to elementsand surfaces that constrain relative motion between two parts, typicallyrotation or linear movement. Bearings may be classified broadlyaccording to the motions they allow and according to their principle ofoperation as well as by the directions of applied loads they can handle.In the context of the instant invention, the bearing surface at issuearises at the interface between the outer surface of the sphericaldistal end of the tubular inner member of a conventional shaver bladeassembly and the corresponding inner surface of the spherical distal endof the tubular outer member of the conventional shaver blade assembly.

The instant invention has both human medical and veterinaryapplications. Accordingly, the terms “subject” and “patient” are usedinterchangeably herein to refer to the person or animal being treated orexamined. Exemplary animals include house pets, farm animals, and zooanimals. In a preferred embodiment, the subject is a mammal.

Hereinafter, the present invention is described in more detail byreference to the Figures and Examples. However, the following materials,methods, figures, and examples only illustrate aspects of the inventionand are in no way intended to limit the scope of the present invention.For example, while the present invention makes specific reference toarthroscopic shaver blade assemblies, it is readily apparent that theteachings of the present invention may be applied to other minimallyinvasive cutting instruments and are not limited to arthroscopic usesalone. As such, methods and materials similar or equivalent to thosedescribed herein can be used in the practice or testing of the presentinvention.

Prior Art Shavers

FIGS. 1 through 5 depict a conventional prior art arthroscopic shaverblade assembly 1 having an outer member 2, having an elongate tubulardistal portion 4, typically formed from a rigid material such as metalor hard plastic, and a proximal hub portion forming a hub assembly 6suitable for mounting in a shaver handpiece. Outer member hub assembly 6includes a hub 8 and retainer 10. Tubular portion 4 includes a distalportion 12 in which is formed cutting window 14 and spherical innerdistal surface 16. Distance 18 extends from the distal end of key 20 ofhub 8 to the distal-most point of spherical inner surface 16. Shaverblade assembly 1 also includes an inner member 32, having an elongatetubular distal portion 34, which, like the tubular portion of the outermember is also typically formed from a rigid metallic or polymericmaterial, and a proximal hub portion forming a hub assembly 38 suitablefor transmitting rotational motion to inner member 32 by means of anexternal handpiece (not shown). Tubular portion 34 includes a distalportion 40 in which is formed cutting window 42 and a distal sphericalsurface 44. Diameter 46 of tubular portion 34 of inner member 32 isslightly less than the diameter of the inner lumen of tubular portion 4of outer member 2 such that that inner member 32 may be rotatablypositioned therein for use. Hub assembly 38 includes hub 48, spring 50and spring retainer 52. Distance 54 extends from the distal-most surfaceof hub 48 to the distal-most point on distal spherical surface 44. Whenmounted in a suitable handpiece, drive tang 56 of hub 48 engages a slotin a driveshaft of the handpiece and spring retainer 52 engages ashoulder on the shaft so as to compress spring 50. Compression of spring50 ensures that distal spherical surface 44 of inner member 32 is infirm contact with spherical inner surface 16 of outer member 2, surfaces44 and 16 forming a distal bearing which axially positions inner member32 within outer member 2. Distances 18 and 54 are selected so that thedistal surface 67 of inner hub 48 is displaced from proximal surface 66of outer hub 8 to form axial gap 68.

During use, tubular portion 34 of inner member 32 is rotated withintubular portion 4 of outer member 2 in an oscillatory manner; that is,the inner member is rotated in one direction a predetermined number ofrevolutions, stopped, and then rotated in the opposite direction apredetermined number of revolutions. This action is repeated as long asthe handpiece in which the shaver blade assembly is mounted isactivated. Suction may be supplied to the lumen of tubular portion 34 ofinner member 32 by means of a passage 58 in inner hub 48 incommunication therewith. Suction draws tissue into contact with, andpartially into, the opening formed by angular alignment of cuttingwindows 14 and 42. Continued rotation of inner member 32 causes tissueto be cut by the cooperative action of the cutting edges of cuttingwindows 14 and 42.

Additional information on shaver construction and operation may be foundin U.S. Pat. No. 5,693,063 (Van Wyk et al.), U.S. Pat. No. 5,766,199(Heisler et al.), and U.S. Pat. No. 5,843,106 (Heisler), the contents ofwhich are incorporated by reference herein in their entirety.

Prior art shavers like shaver 1 are used at rotational speeds as high as5,000 rpm. Since there is essentially point contact between the distalspherical surfaces 44 and 16 and the distal bearing formed thereby issubjected to axial force from spring 50, the distal bearing is subjectedto high hertzian stresses. When a shaver is used at high speeds, thesehigh hertzian stresses may cause cold welding and galling which, inturn, create metallic debris that may be deposited into the surgicalsite. Prevention of galling and debris generation is a major concern forshaver blade manufacturers. Spherical surfaces 44 and 16 must havesmooth finishes free from irregularities. External spherical surface 44are most frequently finished by grinding with a grinding wheel having aperiphery formed to the radius of the surface. Internal sphericalsurface 16 is generally formed by reaming. Surfaces 44 and 16 must alsobe precisely formed so that sliding contact does not occur, forinstance, near the tangencies at which the surfaces are joined to thecylindrical surface of the tubes. Rubbing in these tangency areasfrequently causes galling since the relative velocity between thesurfaces is much higher than at the distal-most point of the radii.Accordingly, surfaces 44 and 16 are generally formed to tolerances ofabout ±0.0002 inches. The forming of surfaces 44 and 16 to these closetolerances, and their inspection to ensure that they are tospecification are both costly aspects of manufacture.

Prevention of galling at the distal bearing point can also be preventedor minimized through the selection of gall-resistant material for one ofthe bearing surfaces, through the selection of materials which can behardened, or through the coating of one of the surfaces with a hardcoating such as chromium, or a lubricious coating such as silver orsilver with silicon. These methods also significantly increase theshaver blade costs.

Some specialty shaver blade assemblies having tubular inner members havedistal bearing surfaces that are not spherical. Such blades, whichgenerally have a flat portion on their closed distal end and arecollectively known as “end cutting” shavers, are generally used fortrimming meniscus in knees, the corners of the inner cutting windowsbeing useful for penetrating tough meniscal tissue and preventing itfrom being ejected from the closing cutting window. However, the distalbearing formed by the planar portions of the distal end wall is stillsubject to the same galling problems as shavers having spherical distalbearing surfaces.

The present invention contemplates the elimination of or modification tothe distal bearing surface while retaining the benefits of shavers thatutilize vacuum pressure to draw tissue into the cutting window. In thismanner, the present invention provides for an improvement in cuttingefficiency while at the same time reducing manufacturing costs.

In one embodiment, this goal is achieved by removing the closed distalend of either the inner member or the outer member that ischaracteristic of conventional shaver assemblies. This embodiment isdescribed in further detail with reference to FIGS. 6 to 16. FIGS. 6 to12 depict an illustrative example of an “open-ended outer” (referred toherein as “OEO”) shaver blade assembly formed in accordance with theprinciples of the present invention. In contrast, FIGS. 13 to 16 depictan illustrative example of an “open-ended inner” (referred to herein as“OEI”) shaver blade assembly formed in accordance with the principles ofthe present invention.

In another embodiment, this goal is be achieved by mitigating the axialconstraints on the inner member that are characteristic of conventionalshaver assemblies. This embodiment is described in further detail withreference to FIGS. 17 to 22. FIGS. 17-19 depict one illustrative exampleof a “free-floating” shaver blade of the present invention. An alternateexample of a “free-floating” shaver blade of the present invention,including a proximal spacer element, is depicted in FIGS. 20 and 21. Afurther alternate example of a modified shaver assembly of the presentinvention, including the combination of a proximal spacer and coilspring, is depicted in FIG. 22.

Open Ended Shavers

As noted previously, it is a goal of the present invention to eliminateor modify the distal bearing surface of an endoscopic cutting instrumentwhile retaining the benefits of shavers that utilize vacuum pressure todraw tissue into the cutting window, to thereby improve cuttingefficiency while at the same time reduce manufacturing costs. Asdiscussed in greater detail below, this goal may be achieved by means ofan “open-ended shaver”.

Referring now to FIGS. 6 through 9, FIG. 6A depicts shaver 100 formed inaccordance with the principles of the present invention. Shaver 100 hasan outer member 102, having an elongate tubular distal portion 104,typically formed from a rigid material such as metal or hard plastic,and a proximal hub portion forming a hub assembly 106 suitable formounting in a shaver handpiece. Hub assembly 106 has a hub 108 andretainer 110. Tubular portion 104 has a distal portion 112 provided withan open distal end 116 and a laterally disposed cutting window 114.Shaver 100 also has an inner member 132, having an elongate tubulardistal portion 134, typically formed from a metallic or hard polymermaterial, and a proximal hub portion forming a hub assembly 138 suitablefor transmitting rotational motion provided by a handpiece to innerassembly 132. Tubular portion 134 has a distal portion 140 provided witha laterally disposed cutting window 142 and a distal end sphericalsurface 144. Diameter 146 of distal portion 134 of inner member 132 isslightly less than the diameter of the inner lumen of distal portion 104of outer member 102 such that that inner member 132 may be rotatablypositioned therein for use. Hub assembly 138 includes hub 148, spring150, spring retainer 152, and proximal bearing element 170 mounted tothe distal end of hub 148. Distance 154 extends from the distal-mostsurface of hub 148 to the distal-most point on distal end sphericalsurface 144. When mounted in a suitable handpiece (not shown), drivetang 156 of hub 148 engages a slot in a driveshaft of the handpiece andspring retainer 152 engages a shoulder on the shaft so as to compressspring 150. Compression of spring 150 ensures that the distal surface172 of bearing element 170 contacts proximal surface 166 of outer hub108 so as to establish the axial position of inner assembly 132 relativeto outer assembly 102.

Distal surface 172 of bearing element 170 and proximal surface 166 ofouter hub 108 together form a bearing in the proximal portion of theshaver. Axial force supplied by spring 150 (or other elastic member)causes frictional heating between spacer element 170 and hub 108 whenthe shaver is used with at high rotational speeds. Bearing element 170is formed from a material that will not adhere to hub 108 due toheating, the material typically being a metal, or a high temperaturepolymeric material such as PEEK, or a lubricious polymeric material suchas PTFE.

Because the bearing of shaver 100 is proximally located between innerhub assembly 138 and outer hub assembly 106 rather than at the distalend of the inner and outer tubular members as in prior art shaver 1,precision finishing of distal end spherical surface 144 is not required,and distance 154 need not be a closely controlled dimension. Thesefactors together significantly decrease the manufacturing costs of innermember 132. Also, the elimination of the spherical surface at the distalend of tubular member 104 (corresponding to surface 16 of tubular member4 of prior art shaver 1) decreases the manufacturing cost of outerassembly 102 of shaver 100 compared to assembly 2 of prior art shaver 1.

Shaver 100 operates in a manner analogous to that of prior art shaver 1.Suction supplied to the lumen of distal portion 134 of inner assembly132, via passage 158 in inner hub 148 in communication therewith, drawstissue into contact with, and partially into, the opening formed byangular alignment of windows 114 and 142. Continued rotation of innerassembly 132 causes tissue to be cut by the cooperative action of thecutting edges of windows 114 and 142. The portion of inner cuttingwindow 142 formed in the distal end radius does not cut soft tissuesince there is cooperating edge on the outer cutting window 114,however, cutting effectiveness of the rest of cutting window 142 is notaffected. The efficiency of the balance of the cutting edge is, in factincreased since tissue can be sucked into the aligned cutting windowsmore effectively without the restriction created by the closed distalend 12 of prior art shaver 1. The performance of shaver 100 when cuttingbone will be enhanced as the removal of the closed distal end of outertubular member 4 allows the cutting edges of inner window 142 to betteraccess the bony surface. Resection of bone is accomplished by the innercutting edges only and does not require cooperative interaction of theinner and outer cutting edges.

FIGS. 10 through 12 depict the distal portion of an alternate embodimentof open-ended shaver constructed in accordance with the principles ofthe present invention, shaver 200 having features for increasedefficiency when cutting soft tissue. In particular, teeth have beenadded to the edges of cutting windows 214 and 242 to prevent tissue frombeing ejected from the cutting window as the edges approach. Also,distal end 216 of the outer tubular member 204 protrudes distance 280beyond the tangency of distal radial surface 244 of inner tubular member234. This causes a larger portion of the tissue sucked into inner window242 to be cut by window 214 of outer member 204.

Shaver 100 and 200 described above are comprised of relatively slidable,cooperating inner and outer elongate tubular members, wherein the innermember is analogous to conventional inner member shaver bladedassemblies, being provided with a distal end spherical surface andlaterally disposed cutting window proximal thereto, while the outermember is modified to have a open, typically blunt-ended distal end anda laterally disposed cutting window integral with or proximal to theopen distal end. Accordingly, these embodiments of open-ended shaver arereferred to as an “open ended outer” or “OEO” shavers.

An alternate embodiment of open-ended shaver is depicted in FIGS. 13 to16. Like OEO shavers 100 and 200, shaver 300 is comprised of relativelyslidable, cooperating inner and outer elongate tubular members. However,in shaver 300, it is the outer member that is analogous to conventionalshaver blade assemblies, being provided with a distal end sphericalsurface and laterally disposed cutting window proximal thereto, whilethe inner member is modified to have a open, typically blunt-endeddistal end and a laterally disposed cutting window integral with orproximal to the open distal end. Accordingly, the embodiment ofopen-ended shaver depicted in FIGS. 13 to 16 is referred to as an “openended inner” or “OEI” shaver.

Referring now to FIGS. 13 through 16, FIG. 13 depicts an OEI shaver 300formed in accordance with the principles of the present invention.Shaver 300 has an outer member 302, having an elongate tubular distalportion 304, typically formed from a rigid material such as metal orhard plastic, and a proximal hub portion forming a hub assembly 306suitable for mounting in a shaver handpiece. Hub assembly 306 has a hub308 and retainer 310. Tubular portion 304 has a distal portion 312provided with a distal end spherical surface 316 and a laterallydisposed cutting window 314. Shaver 300 also has an inner member 332,having an elongate tubular distal portion 334, typically formed from ametallic or hard polymer material, and a proximal hub portion forming ahub assembly 338 suitable for transmitting rotational motion provided bya handpiece to inner assembly 332. Tubular portion 334 has a distalportion 340 provided with a laterally disposed cutting window 342 and anopen distal end surface 344. Diameter 346 of distal portion 334 of innermember 332 is slightly less than the diameter of the inner lumen ofdistal portion 304 of outer member 302 such that that inner member 332may be rotatably positioned therein for use. Hub assembly 338 includeshub 348, spring 350, spring retainer 352, and proximal bearing element370 mounted to the distal end of hub 348. When mounted in a suitablehandpiece (not shown), drive tang 356 of hub 348 engages a slot in adriveshaft of the handpiece and spring retainer 352 engages a shoulderon the shaft so as to compress spring 350. Compression of spring 350ensures that the distal surface 372 of bearing element 370 contactsproximal surface 366 of outer hub 308 so as to establish the axialposition of inner assembly 332 relative to outer assembly 302.

Distal surface 372 of bearing element 370 and proximal surface 366 ofouter hub 308 together form a bearing in the proximal portion of theshaver. Axial force supplied by spring 350 (or other elastic member)causes frictional heating between spacer element 370 and hub 308 whenthe shaver is used with at high rotational speeds. Bearing element 370is formed from a material that will not adhere to hub 308 due toheating, the material typically being a metal, or a high temperaturepolymeric material such as PEEK, or a lubricious polymeric material suchas PTFE.

Because the bearing of shaver 300 is proximally located between innerhub assembly 338 and outer hub assembly 306 rather than at the distalend of the inner and outer tubular members as in prior art shaver 1,precision finishing of distal end surface 344 is not required, anddistance 382 need not be a closely controlled dimension. These factorstogether significantly decrease the manufacturing costs of outer member302. Also, the elimination of the spherical surface at the distal end340 of inner tubular member 334 (corresponding to surface 44 of tubularmember 34 of prior art shaver 1) decreases the manufacturing cost ofinner member 332 of shaver 300 compared to member 32 of prior art shaver1.

Shaver 300 operates in a manner analogous to that of prior art shaver 1as well as the previously described shavers 100 and 200 of the presentinvention. Suction supplied to the lumen of distal portion 334 of outerassembly 332, via passage 358 in inner hub 348 in communicationtherewith, draws tissue into contact with, and partially into, theopening formed by angular alignment of windows 314 and 342. Continuedrotation of inner assembly 332 causes tissue to be cut by thecooperative action of the cutting edges of windows 314 and 342.

Free-Floating Shavers

As noted previously, it is a goal of the present invention to eliminatethe distal bearing surface of an endoscopic cutting instrument whileretaining the benefits of shavers that utilize vacuum pressure to drawtissue into the cutting window, to thereby improve cutting efficiencywhile at the same time reduce manufacturing costs. As discussed ingreater detail below, this goal may be achieved by means of a“free-floating shaver”. The free-floating shavers of the presentinvention are analogous to conventional endoscopic shavers with oneimportant exception: the axial constraints characteristic ofconventional shavers have been substantially reduced or eliminated. Inone embodiment, this is achieved by eliminating the spring and springretainer characteristic of conventional shaver assemblies, therebyallowing the inner member to move axially in an unrestricted fashion,within predetermined limits.

Proximal movement of the inner member may be limited by one ore morecoordinating features in the handpiece, the inner hub and/or in theouter hub. For example, the ability of the inner member to movelaterally in the proximal direction is constrained at least in part bythe fact that the outer hub assembly and the handpiece assembly arefirmly locked together, typically via interaction between outer hub keyelement and a coordinating lock element in the handpiece assembly. Thislocked configuration firmly establishes the distance between the outerhub and the handpiece drive member, thereby preventing relative movementthereof. However, additional modifications may be made to further limitthe ability of the inner hub member to travel.

Distal movement of the inner member may be limited by contact betweenthe outer surface of the inner member distal end and the inner surfaceof the outer member distal end, the surfaces functionally as a stoprather than a bearing. I Alternatively, movement of the inner member maybe controlled by means of a proximal spacer or distal limit stoppositioned between the inner and outer hubs. For example, a distal limitstop or proximal spacer may be positioned between the inner and outerhubs such that contact is never made between the inner and outer distalend spherical surfaces.

When the distal limit arises from the use of a proximal spacer, it ispreferable to provide for a predetermined minimum gap between the outersurface of the inner member distal end and the inner surface of theouter member distal end to prevent the formation of a distal bearing.The invention is not limited to any particular ranges of motion.However, for embodiments having one stop at the tip of the bearingsurface and the other at the fork, the range of motion (i.e., thedistance between the inner distal surface of the outer member and theouter distal surface of the inner member) is preferably on the order ofpreferably 0.005 to 0.120 inches, more preferably 0.010 to 0.080 inches.For embodiments that utilize a proximal spacer that prevents “bearingsurfaces” from coming into contact, the front clearance when the innermember is at its axial distal limit should be between 0.002 to 0.100inches, more preferably 0.002 to 0.060, even more preferably 0.005 to0.030 inches. In other words, the total travel distance permitted forthe inner member should be as above, preferably 0.005 to 0.120 inches,more preferably 0.010 to 0.080 inches.

Turning now to FIGS. 17 to 19, FIG. 17A depicts a free floating shaver500 wherein the goals of improved cutting efficiency and reducedmanufacturing costs are achieved by removing the axial constraints ofthe inner member that are characteristic of conventional shaverassemblies. Specifically, FIGS. 17A to 17C depict an illustrative shaver500 formed in accordance with the principles of the present inventionhaving an outer member 502, having an elongate tubular distal portion504, typically formed from a rigid material such as metal or hardplastic, and a proximal hub portion forming a hub assembly 506 suitablefor mounting in a shaver handpiece. Hub assembly 506 has a hub 508 andretainer 510. Tubular portion 504 has a distal portion 512 provided witha distal end spherical surface 516 and a laterally disposed cuttingwindow 514. Shaver 500 also has an inner member 532, having an elongatetubular distal portion 534, typically formed from a metallic or hardpolymer material, and a proximal hub portion forming a hub assembly 538suitable for transmitting rotational motion provided by a handpiece toinner assembly 532. Tubular portion 534 has a distal portion 540provided with a laterally disposed cutting window 542 and a distal endspherical surface 544. Diameter 546 of distal portion 540 of innermember 532 is slightly less than the diameter of the inner lumen ofdistal portion 504 of outer member 502 such that that inner member 512may be rotatably positioned therein for use.

Shaver 500 is identical to prior art shaver 1 with the exception thatspring 50 and spring retainer 52 are optionally eliminated from innermember hub assembly 538. Accordingly, hub assembly 538 simply compriseshub 548, suction passage 558 and drive tang 556. When mounted in asuitable handpiece 2000, drive tang 556 of hub 548 engages a slot 2020in a driveshaft of the handpiece. Because spring 50 is eliminated, innerassembly 532 travels axially freely within outer member 502 withinpredetermined limits of axial motion.

FIGS. 18A to 18B depict shaver 500 with inner assembly 532 at itsdistal-most limit of travel, outer radius 544 of inner assembly 532being in contact with inner radius 516 of outer assembly 502. Alsodepicted in FIGS. 18A and 18B is drive member 2000 of a suitablehandpiece in which shaver 500 is removably mounted. Slot 2020 of member2000 engages with drive tang 556 of hub 548 so as to transmit rotationalmotion from member 2000 to hub 548. Proximal-most surface 580 of hub 548is displaced axially from distal-most surface 2040 of member 2000distance 2100. Distances 2100 and 582 are equal (FIG. 19B).

FIGS. 19A to 19C depict shaver 500 with inner assembly 532 at itsproximal-most limit of travel, proximal-most surface 580 of hub 548being in contact with distal-most surface 2040 of member 2000. Outerradius 544 of inner assembly 532 is displaced proximally distance 582from inner radius 516 of outer assembly 502, a distance that is equal todistance 2100 shown in FIG. 18C.

Because spring 50 of prior art shaver 1 is eliminated, there is no axialloading between distal outer radius 544 of inner member 532 and distalinner radius 516 of outer member 502 such that the radii together do notform a bearing, but rather function as a stop to distally limit axialtravel of inner member 532. Contact between surfaces 516 and 544 isintermittent and has a low contact force. Preload of the bearingsurfaces present in prior art shaver 1 is eliminated.

Because of this, precision finishing of distal end spherical surfaces544 and 516 is not required. This significantly decreases themanufacturing costs of assemblies 532 and 502.

Shaver 500 is used in the same manner as prior art shaver 1. Efficiencyis increased because inner assembly 532 is allowed to float axiallyallowing the cutting edges to follow a path of least resistance whenpenetrating the tissue. In particular, the floating nature of the innermember allows the sharp features (e.g., teeth) of the cutting windows tobetter penetrate the tissue, by allowing them to incrementally yetfreely the axial direction so as to follow a path of least resistance.Because the cutting features more firmly embed themselves in the tissue,less tissue is ejected from the cutting window as the inner and outercutting edges approach each other. Because less tissue is ejected, moreis resected with each window closure, thereby increasing the efficiencyof the blade.

Referring now to FIGS. 20 and 21, FIG. 20A depicts a free floatingshaver 600 wherein the goals of improved cutting efficiency and reducedmanufacturing costs are achieved by removing the axial constraints ofthe inner member that are characteristic of conventional shaverassemblies while at the same time providing a means for preventingfrictional contact between the corresponding distal surfaces of theinner and outer members.

Specifically, FIGS. 20A-20C depict an illustrative shaver 600 formed inaccordance with the principles of the present invention having an outermember 602, having an elongate tubular distal portion 604, typicallyformed from a rigid material such as metal or hard plastic, and aproximal hub portion forming a hub assembly 606 suitable for mounting ina shaver handpiece. Hub assembly 606 has a hub 608 and retainer 610.Tubular portion 604 has a distal portion 612 provided with a distal endspherical surface 616 and a laterally disposed cutting window 614.Shaver 600 also has an inner member 632, having an elongate tubulardistal portion 634, typically formed from a metallic or hard polymermaterial, and a proximal hub portion forming a hub assembly 638 suitablefor transmitting rotational motion provided by a handpiece to innerassembly 632. Tubular portion 634 has a distal portion 640 provided witha laterally disposed cutting window 642 and a distal end sphericalsurface 644. Diameter 646 of distal portion 634 of inner member 632 isslightly less than the diameter of the inner lumen of distal portion 604of outer member 602 such that that inner member 612 may be rotatablypositioned therein for use.

Like free-floating shaver 500, free-floating shaver 600 is identical toprior art shaver 1 with the exception that spring 50 and spring retainer52 are optionally eliminated from inner member hub assembly 638.Accordingly, hub assembly 638 simply comprises hub 648, suction passage658 and drive tang 656. When mounted in a suitable handpiece 2000, drivetang 656 of hub 648 engages a slot 2020 in a driveshaft of thehandpiece. Because spring 50 is eliminated, inner assembly 632 travelsaxially freely within outer member 602 within predetermined limits ofaxial motion. To that end, shaver 600 is provided with a proximal spacerelement 675 disposed between the inner and outer hub assemblies, theproximal spacer having a proximal surface 676 that may engage the distalsurface 667 of the inner hub 648 and a distal surface 677 that mayengage the proximal surface 666 of the outer hub 608, to thereby limitthe axial travel of the inner member 632.

FIGS. 20B to 20C depict shaver 600 with inner assembly 632 at itsproximal-most limit of travel, proximal-most surface 680 of hub 648being in contact with distal-most surface 2040 of member 2000. Outerradius 644 of inner assembly 632 is displaced proximally distance 682from inner radius 616 of outer assembly 602.

FIGS. 21A to 21C depict shaver 600 with inner assembly 632 at itsdistal-most limit of travel, outer radius 644 of inner assembly 632being displaced axially distance 682 from inner radius 616 of outerassembly 602. Also depicted in FIGS. 21A and 21C is drive member 2000 ofa suitable handpiece in which shaver 600 is removably mounted. Slot 2020of member 2000 engages with drive tang 656 of hub 648 so as to transmitrotational motion from member 2000 to hub 648. Proximal-most surface 680of hub 648 is displaced axially from distal-most surface 2040 of member2000 distance 2100, a distance that is equal to distance 668 of FIG.20C.

Because spring 50 of prior art shaver 1 is eliminated, there is no axialcontact between distal outer radius 644 of inner member 632 and distalinner radius 616 of outer member 602 such that the radii together do notform a bearing. Spacer 675 functions as a stop to distally limit axialtravel of inner member 632. Preload of the bearing surfaces present inprior art shaver 1 is eliminated. Because of this, precision finishingof distal end spherical surfaces 644 and 616 is not required. Thissignificantly decreases the manufacturing costs of assemblies 632 and602.

Shaver 600 is used in the same manner as prior art shaver 1. As withfree-floating shaver 500, efficiency is increased with shaver 600because inner assembly 632 is allowed to float axially allowing thecutting edges to follow a path of least resistance when penetrating thetissue. In particular, the floating nature of the inner member allowsthe sharp features (e.g., teeth) of the cutting windows to betterpenetrate the tissue, by allowing them to incrementally yet freely theaxial direction so as to follow a path of least resistance. Because thecutting features more firmly embed themselves in the tissue, less tissueis ejected from the cutting window as the inner and outer cutting edgesapproach each other. Because less tissue is ejected, more is resectedwith each window closure, thereby increasing the efficiency of theblade.

Proximal Bearing Shavers

Referring now to FIG. 22, FIG. 22A depicts a modified shaver 700 whereinthe goals of improved cutting efficiency and reduced manufacturing costsare achieved by limiting the axial constraints of the inner member thatare characteristic of conventional shaver assemblies while at the sametime providing a means for preventing frictional contact between thecorresponding distal surfaces of the inner and outer members.

Specifically, FIGS. 22A-22C depict an illustrative shaver 700 formed inaccordance with the principles of the present invention having an outermember 702, having an elongate tubular distal portion 704, typicallyformed from a rigid material such as metal or hard plastic, and aproximal hub portion forming a hub assembly 706 suitable for mounting ina shaver handpiece. Hub assembly 706 has a hub 708 and retainer 710.Tubular portion 704 has a distal portion 712 provided with a distal endspherical surface 716 and a laterally disposed cutting window 714.Shaver 700 also has an inner member 732, having an elongate tubulardistal portion 734, typically formed from a metallic or hard polymermaterial, and a proximal hub portion forming a hub assembly 738 suitablefor transmitting rotational motion provided by a handpiece to innerassembly 732. Tubular portion 734 has a distal portion 740 provided witha laterally disposed cutting window 742 and a distal end sphericalsurface 744. Diameter 746 of distal portion 734 of inner member 732 isslightly less than the diameter of the inner lumen of distal portion 704of outer member 702 such that that inner member 712 may be rotatablypositioned therein for use.

Unlike free-floating shavers 500 and 600, modified shaver 700 includesthe spring and spring retainer that are characteristic of prior artshaver assemblies. Accordingly, hub assembly 738 comprises hub 748,suction passage 758, drive tang 756, spring 750 and spring retainer 752.When mounted in a suitable handpiece (not shown), drive tang 756 of hub748 engages a slot in a driveshaft of the handpiece and spring retainer752 engages a shoulder on the shaft so as to compress the spring.Compression of spring places pressure on inner tubular member, urgingits distal toward the inner distal surface of the outer member. However,shaver 700 is provided with a proximal spacer element 775 disposedbetween the inner and outer hub assemblies, the proximal spacer having aproximal surface 776 that may engage the distal surface 767 of the innerhub 748 and a distal surface 777 that may engage the proximal surface766 of the outer hub 708, to thereby limit the axial travel of the innermember 732.

FIGS. 22B to 22C depict shaver 700 with inner assembly 732 at itsdistal-most limit of travel, outer radius 744 of inner assembly 732being displaced axially a distance of 782 from inner radius 716 of outerassembly 702. Because action of spring 750 of shaver 700 is restrictedby means of the proximal space, there is no axial loading between distalouter radius 744 of inner member 732 and distal inner radius 716 ofouter member 702 such that the radii together do not form a bearing, theproximal spacer distally limiting axial travel of inner member 732.Preload of the bearing surfaces present in prior art shaver 1 iseliminated. Because of this, precision finishing of distal end sphericalsurfaces 744 and 716 is not required. This significantly decreases themanufacturing costs of assemblies 732 and 702.

INDUSTRIAL APPLICABILITY

As noted previously, the present invention is directed to minimallyinvasive endoscopic cutting instrument having improved cuttingefficiency and reduced manufacturing costs. In particular, by increasingtissue access to the cutting window and/or reducing tissue ejection, thepresent invention provides for improved cutting efficiency. Likewise, byeliminating or modifying the distal end axial bearing surfaces, thepresent invention provides for a substantial reduction in manufacturingcosts.

The disclosure of each publication, patent or patent applicationmentioned in this specification is specifically incorporated byreference herein in its entirety. However, nothing herein is to beconstrued as an admission that the invention is not entitled to antedatesuch disclosure by virtue of prior invention.

The invention has been illustrated by reference to specific examples andpreferred embodiments. However, it should be understood that theinvention is intended not to be limited by the foregoing description,but to be defined by the appended claims and their equivalents.

1. An endoscopic surgical assembly comprising concentrically disposedelongated tubular inner and outer members, each of said elongatedmembers comprising a coordinating hub disposed at its proximal end, alaterally disposed cutting aperture at its distal end, and a centrallumen extending between the two ends, said inner member being sized tobe slidably received within the lumen of said outer member, wherein:when said inner and outer hubs are connected, axial displacement betweenthe inner and outer members is fixed and the respective cuttingapertures of said inner and outer members are aligned to permitcooperative resection of tissue in contact with said apertures, furtherwherein: (a) the inner member comprises a, distally facing open endwhile the distally facing end of the outer member comprises a closedsurface, or (b) the outer member comprises a, distally facing open endwhile the distally facing end of the inner member comprises a closedsurface.
 2. The surgical assembly of claim 1, wherein said closedsurface comprises a spherical surface. 3 The surgical assembly of claim1, wherein the distally facing open end comprises a blunt surface. 4.The surgical assembly of claim 1, wherein the distally facing open endcomprises an angled surface.
 5. The surgical assembly of claim 1,wherein the cutting aperture of the closed-ended member is proximallyspaced from the spherical distal end.
 6. The surgical assembly of claim1, wherein the cutting aperture of the open-ended member is proximallyspaced from the open distal end.
 7. The surgical assembly of claim 1,wherein the cutting aperture of the open-ended member is integral withthe open distal end.
 8. The endoscopic surgical assembly of claim 1,further comprising an elastic member that transmits an axial forcedistally on the inner member to maintain contact between a distalsurface of the inner hub and a proximal surface of the outer hub whensaid inner and outer hubs are connected such that the distal ends of theinner and outer members do not form a distal bearing surface.
 9. Theendoscopic surgical assembly of claim 8, wherein said elastic membercomprises a coiled spring affixed to the inner hub.
 10. The assembly ofclaim 1, wherein each of said cutting apertures has a perimetercomprised of two longitudinal cutting edges at least one transversecutting edges.
 11. The assembly of claim 10, wherein one or more of saidcutting edges are beveled.
 12. The assembly of claim 11, wherein one ormore of said beveled cutting edges are provided with plurality of teeth.13. The assembly of claim 12, wherein the angle of said beveled cuttingedges ranges from 15 to 70 degrees.
 14. An endoscopic surgical assemblycomprising concentrically disposed tubular elongated inner and outermembers, each of said elongated members comprising a coordinating hubdisposed at its proximal end, a laterally disposed cutting aperture atits distal end, and a central lumen connecting the two, said innermember being sized to be slidably received within the lumen of saidouter member, wherein axial force on said inner member is eliminated andsaid inner member is permitted to move axially within predeterminedlimits, further wherein when said inner and outer hubs are connected,the respective cutting apertures of said inner and outer members arealigned to permit cooperative resection of tissue in contact with saidapertures but the distal ends of the inner and outer members do not forma distal bearing surface.
 15. The endoscopic surgical assembly of claim14, further wherein the inner member hub is free from axial pressuremeans, thereby eliminating axial pressure on said inner member.
 16. Theendoscopic surgical assembly of claim 15, wherein said axial pressuremeans comprises an elastic member or coil spring.
 17. The endoscopicsurgical assembly of claim 14, wherein the proximal end of the outermember hub is characterized by an outer collar concentrically disposedabout an inner stem, said assembly further comprising an annular spacerelement positioned between the proximal end of the inner stem and thedistal end of the inner member hub so as to prevent direct contacttherebetween.
 18. The surgical assembly of claim 14, wherein each ofsaid cutting apertures has a perimeter comprised of two longitudinalcutting edges at least one transverse cutting edges.
 19. The assembly ofclaim 18, wherein one or more of said cutting edges are beveled.
 20. Theassembly of claim 19, wherein one or more of said beveled cutting edgesare provided with plurality of teeth.
 21. The assembly of claim 20,wherein the angle of said beveled cutting edges ranges from 15 to 70degrees.
 22. An endoscopic surgical assembly comprising concentricallydisposed elongated tubular inner and outer members, each of saidelongated members comprising a coordinating hub disposed at its proximalend, a laterally disposed cutting aperture at its distal end, and acentral lumen connecting the two, said inner member being sized to beslidably received within the lumen of said outer member, wherein: (a)the inner member hub includes an elastic member that transmits an axialforce distally on said inner member so as to constrain proximal movementthereof; (b) the proximal end of the outer member hub is characterizedby an outer collar concentrically disposed about an inner stem, saidassembly further comprising an annular spacer element positioned betweenthe proximal end of the inner stem and the distal end of the innermember hub so as to prevent direct contact therebetween; and (c) whensaid inner and outer hubs are connected, the respective cuttingapertures of said inner and outer members are aligned to permitcooperative resection of tissue in contact with said apertures but thedistal ends of the inner and outer members do not form a distal bearingsurface.
 23. The surgical assembly of claim 22, wherein each of saidcutting apertures has a perimeter comprised of two longitudinal cuttingedges at least one transverse cutting edges.
 24. The assembly of claim23, wherein one or more of said cutting edges are beveled.
 25. Theassembly of claim 24, wherein one or more of said beveled cutting edgesare provided with plurality of teeth.
 26. The assembly of claim 25,wherein the angle of said beveled cutting edges ranges from 15 to 70degrees.
 27. A method for resecting a target tissue within a surgicalsite of interest comprising the steps of: (i) introducing the endoscopicsurgical assembly of claim 14 into the surgical site; (ii) rotating theinner member relative to the outer member, wherein the relativerotational movement of the members results in relative rotationalmovement of their respective apertures which cooperate to cut the targettissue; and (iii) allowing the inner member to float unconstrained in anaxial dimension, which, in turn, allows the inner member cuttingaperture to find the region of target tissue that is least resistant toresection so as to minimize the ejection of tissue from the coordinatingcutting apertures.
 28. The method of claim 27, further comprising thestep of rotating said inner member relative to said outer tubular memberin one direction for a first predetermined number of revolutions thenrotating said inner member relative to said outer tubular member in anopposite direction for a second predetermined number of revolutions. 29.The method of claim 27, further comprising the step of applying suctionto the proximal end of the surgical assembly so as to draw target tissueinto contact with the cooperating cutting windows and aspirate resectedtissue from the surgical site through the central lumen of said innertubular member.